Archaeologists diving into a lake in the crater of a snowcapped volcano found wooden scepters shaped like lightning bolts that match 500-year-old descriptions by Spanish priests and conquerors writing about offerings to the Aztec rain god.

Today’s tax codes are complicated, but the ancient Aztecs likely shared your pain. To measure tracts of taxable land, Aztec mathematicians had to develop their own specialized arithmetic, which has only now been decoded.